In a network evolution process, for example, in a network reconstruction evolution process of a metropolitan area network, an original fixed network service is borne by a Synchronous Digital Hierarchy (SDH) device. A newly established mobile service is borne by an Internet Protocol (IP) device. The two types of services may coexist in a quite long time. Therefore, a hybrid service bearing device needs to bear multiple types of services at the same time.
An SDH service requires the hybrid service bearing device to establish a top-down frequency synchronization network. The mobile service requires, in a Long Term Evolution-Advanced (LTE-A) age, the hybrid service bearing device to have a capability of bearing a synchronous Ethernet and 1588v2 clock, and be capable of obtaining frequency synchronization and time synchronization from a Global Navigation Satellite System (GNSS). In addition, the hybrid service bearing device may further need to support a synchronization network evolved to higher precision in the future. Different synchronization networks may have different precision and different clock sources. Currently, the hybrid service bearing device can only separately transfer data of multiple different types of services to corresponding devices and cannot simultaneously transfer clock signals generated by clock sources of multiple different types of services. With evolution of wireless technologies and fixed network technologies, a demand for supporting, by a network device, multiple different clock domains becomes increasingly popular.
The International Telecommunication Union Telecommunication Standardization Sector (ITU-T) defines reference models of various synchronization network devices but does not define how to bear clock signals of multiple different clock domains using a same device simultaneously.